I couldn't agree with you more about christmas valley. I went there with a few of my buddies last year, and what a waist of time. First of is the horrible road into the place. If there is anything loose on your vehicle on the way in, it will probably fall off on the way out. Then there's then dunes themselves, small and very dusty/dirty, it's like riding in powder.
I would definitely make sure to hit any of the dunes on the Oregon Coast, they all off a little something different. When are you heading out??
Requirements 95 DB or less, Flag, Off road Permit, and a NW Forest pass for the parking lots. Definitely recommend paddles